JP Patent Kokai Publication No.2005-025914 (Patent Literature 1) discloses a nonvolatile semiconductor memory device (what is called resistive random access memory), where difference in resistance value of variable resistance elements corresponds to a logical value (data “0” or data “1”), and variable resistance elements are used as memory cells. Control with regard to the resistive random access memory disclosed in Patent Literature 1, for example, has current flow in opposite directions when writing (data “1”) and when erasing (data “0”), and the amount of current thereof corresponds to the data, as shown in FIG. 9 and FIG. 11 of Patent Literature 1.
JP Patent Kokai Publication No.2012-069220 (Patent Literature 2) discloses a semiconductor memory device provided with a variable resistance element in which it is possible, in a random access writing operation, to write stably and with good control to a desired resistance state.
The respective disclosures of the abovementioned cited literatures are incorporated herein by reference thereto. The following analysis is given by the present inventors.
According to a control method disclosed in Patent Literature 1, it is possible to write desired data to a resistive random access memory. However, even if this control is executed, it is difficult to correctly write the desired data by performing write control once. As a result, in actuality, similar to flash memory and the like, in many cases the abovementioned write control is performed repeatedly, while performing verification by a verify operation.
Here, variation in resistance value of a variable resistance element is due to a process in which a current flows in the variable resistance element. Accordingly, with regard to control concerning where a current larger than necessary flows in the variable resistance element or where the number of times the current is made to flow is large, there is a possibility of an adverse effect occurring such that the lifespan of the variable resistance element is shortened or a time-related degradation characteristic deteriorates. Therefore, it is desired to have a semiconductor device that uses a variable resistance element that contributes to completing a data write operation in a suitable number of times and without more current than necessary being made to flow.